Circuitry for timekeeping instruments



4 Sept.24,1968 K. A.SPARING v 3,403,312

CIRCUITRY FOR TIMEKEEPI NG INSTRUMENTS Filed Dec. 20, 1965 l NVEN TOR. KLAUS ASBQRING A T TORNE Y8.

United States Patent 3,403,312 CIRCUITRY FOR TIMEKEEPING INSTRUMENTS Klaus A. Sparing, Dusseldorf, Germany, assignor to The United States Time Corporation, Waterbury, Conu., a corporation of Connecticut Filed Dec. 20, 1965, Ser. No. 514,971 Claims priority, application Germany, Jan. 2, 1965,

9 Claims. of. 318-130) ABSTRACT OF THE DISCLOSURE A battery-driven timepiece includes a mechanical oscillator as its time base. The oscillator is driven by the interaction of a magnet and a coil. The coil is pulsed by a free running multivibrator circuit having a pair of complementary transistors. The coil is in series with the collector-emitter pairs of both transistors and the battery.

The present invention relates to timekeeping instruments, and more particularly to a battery drlven watch.

The prior art includes many electronic circuits adapted for timekeeping. In one such circuit, U.S. Patent 3,046,- 460, an oscillative coil acts as a pick-up coil and drive coil and cooperates with several stationary, permanent magnets. This coil is a part of a monostable multlvlbrator circuit. This circuitry shows two transistors arranged complementary to each other, i.e. PNP and NPN, and a battery source.

In this arrangement both transistors are continuously blocked in the rest position of the vibrator. Therefore, this system is not self-starting. During the mechanical vibrations of the system both transistors are opened by the impulse generated in the coil, however, the coil current flows only through one transistor. Another current flows through the other transistor parallel to it which is useless for the impulse, in a considerable amount of at least 20% or more of the total current. This means that a specific battery has a shorter lifetime or that for a determined lifetime a larger battery has to be used.

It is an objective of the present invention to provide an electric circuit for a timepiece which is relatively inexpensive, has few parts, is small and has a relatively low battery consumption.

In accordance with the present invention the timepiece of this invention includes at least one permanent magnet and an oscillating coil acting as a pick-up coil as well as a drive coil. The coils are part of a multivibrator circuitry-consisting of two complementary transistors, one RC network and a current source. The magnet and the coil are part of an oscillating system and causes its impulse. The total coil current flows through the exit sides of both transistors and only a very small part is branched off for triggering and does not impulse the coil. Thereby one obtains an optimum efliciency and a maximum lifetime of the battery, which is an important advantage for wrist watches.

A damping condenser can be provided which preferably will be in parallel with the coil for the suppression of vibrations of high frequency.

It is furthermore advantageous to connect a resistor between the base of the transistor and the coil. This circuitry becomes unstable due to this resistor, which means that a constant, electric vibration occurs independently from the relative motion between coil and magnet.

Since this unstable electrical system causes vibration by itself, without a physical impulse from the outside, the mechanical vibration system of the timekeeping instrument starts by itself. This is an advantage since, under Patented Sept. 24, 1968 unfavorable conditions, such a mechanical system can come to a stop for a short time due to external influences such as shock.

The self-starting and also the vibration impulse of the circuitry are particularly favorable when the resistor is a multiple of the ohmic resistance of the coil. In order that the mechanical vibration system performs synchronization of the circuitry, the frequency of the free running, unstable multivibrator should be lower (at maximum equal) than the inherent mechanical frequency of the vibrating system.

Other objectives of the present invention will be apparent from the description of the preferred embodiment of the invention described below in conjunction with the accompanying drawing. The drawing shows schematically a form of construction of the invention.

A permanent magnet, 10, is fixed on the free end of a spring 12. The oposite end of the spring is firmly connected with a stationary part. The magnet 10 vibrates forwards and backwards, corresponding to the double arrow A. The magnet 10 cooperates with a stationary coil 14 which serves simultaneously as a pickup coil and drive (impulse) coil. In this connection it should be mentioned that only for reason of easier representation the magnet is shown as movable, but usually the magnet is stationary and the coil is oscillative.

One end of the coil 14 is connected to the plus termial of a DC. (battery) source 16. The minus terminal of the DC. source is connected over the collector-emitter path of a PNP transistor 18. The emitter-collector path of an NPN transistor 20 is connected with the other end of the coil 14. Both transistors 18 and 20 can be exchanged against each other, only the battery terminals would then have to be changed correspondingly. Another current circuit leads from the plus terminal to the DC. source over a resistor 22 to the base of the transistor 20, from there over the emitter of the transistor 20, the emitter of the transistor 18, the base of the transistor 18 and finally over a resistor 24 to the minus terminal of the current source. Furthermore, the base of the transistor 18 is connected over a condenser 26 with the collector of the transistor 20 and with one end of the coil 14.

Another condenser 30, shown by a dash dotted line, may be provided which suppresses high frequency current. It is arranged parallel to the coil 14.

In the following the mode of action of the circuit will be explained in detail.

In the rest position, when magnet 10 is not moving the current source 16 is switched on by a switch (not shown). Condenser 26 begins to charge over the charging circuit formed by the coil 14 and the resistor 24, the condensor 26 can be charged up to the voltage of the current source. A negative voltage is therefore placed on the base of the transistor 18, which means the DC. voltage acts on the collector so that the transistor 18 becomes conductive. The base of the transistor 20 has applied to it the full positive voltage of the current source 16, so that the base and the collector have the same voltage, which means the transistor 20 is open (is ready to conduct).

As soon as both transistors 18 and 20 start to be open, a current from the current source 16 begins to flow over the coil 14 and the collector-emitter paths of both transistors 18 and 20. A reciprocal physical impulse effect between the coil 14 and the magnet 10 occurs and, in the present example, an impulse will be given to the magnet 10.

Since also the collector-emitter path of the transistor 18 becomes conductive, the condensor 26 can be discharged through the emitter-base-path of the transistor 18. Due to the transistor 18 the vibration avalanches at the full height of the impulse. After the discharge of the condenser 26 the impulse collapses avalanche like. By this relative motion'between coil and magnet and the mechanical inherent frequency of the vibrating system, a control impulse is induced in the coil.

The condition after the starting vibration will now be explained.

When no impulse is induced in the coil 14 after the mechanical start of vibration, the transistor 18 is blocked because the base of transistor 18 is more positive than the collector, The same is true of the transistor 20, since at the closed transistor 18 no governing current can flow through the base. With the presence of the resistor 22 the transistor is also blocked because its base is more negative than the collector.

When an impulse is created in the coil 14 the base of the transistor 18 is controlled by means of the condensor 26 and transistor 18 will be opened. Now a corresponding current can flow over the base-emitter path of th transistor 20 so that the current circuit from the coil 14 through the transistor 20, transistor 18 to the source of the current 16 is closed. The impulse current necessary for the impulse of the vibrating system is flowing.

The dimensioning of the particular components is such that from the entrance (base of the transistor 18) up to the exit (collector of the transistor 20) the phase will be rotated for 360 so that the general condition of vibration will be satisfied.

The length of impulse is determined by the characteristic of the rate of discharge of the condenser 26, which is discharged over both transistors. After the discharge of the condenser the preceding condition appears again, this means the more positive base compared to the collector blocks the transistor 18, and, by that, also the transistor 20.

The interval between the electric impulses is determined by the characteristic of the rate of charge of the condenser. According to the present invention the condenser is chosen so that its discharge is longer, or at most equal, to the period of the mechanical vibration system. The synchronization and triggering of the impulse circuitry will therefore occur by the mechanical vibration system. I

The resistor 24 is relatively large e.g. in the magnitude of 1M ohm and the resistor 22 is of a smaller magnitude, for example of 100K ohm. The capacitor 26 is in the magnitude of microfarad.

By the indicated values and using appropriate transistors and an appropriate coil, mechanical vibration systerns in a frequency range of between 200 and 500 periods per second can be synchronized Without harming the phase condition.

Modifications may be made in the present invention within the scope of the subjoined claims. For example, as already mentioned either the coil or magnet, or both, may be movable.

I claim:

1. A timepiece including at least one permanent magnet, a single coil having a first and a second end, said coil acting as a pick-up coil and as a drive coil, means to physically oscillate the magnet relative to the coil, a source of direct current, and a multivibrator circuit consisting of first and second complementary transistors, wherein the magnet and the coil are part of a mechanical oscillating system and drive said system, means to transmit impulses from the coil to the base of the first transistor, the collector of the second transistor being connected to said second end of the coil, the collector of the first transistor being connected to the current source, and the first end of the coil being connected to said current source, said coil being in series with the collectoremitter paths of said transistors and with said current source.

2. A timepiece according to claim 1, wherein a damping condensor is provided across the coil for the suppression of high frequency oscillations.

3. A timepiece according to claim 1, wherein between the base of the first transistor and said second end of the coil a resistor is connected.

4. A timepiece according to claim 3, wherein the resistor is a multiple of the ohmic resistance of the coil.

5. A timepiece according to claim 1 wherein the parameters are dimensioned such that the frequency of the free running, multivibrator is at maximum as high as the mechanical inherent frequency of the vibratin system.

6. A timepiece as in claim 1 wherein the means to transmit impulses from the coil to the base of the first transistor includes a capacitor connected between said base and said first side of said coil.

7. A timepiece including a permanent magnet, a single coil having a first and a second end,.said coil acting as a pick-up and a drive coil, means to physically oscillate the magnet relative to the coil, a source of direct current, and a circuit having substantially zero phase shift, including first and second complementary transistors, said first transistor being arranged in a common-collector configuration with zero phase shift, said second transistor being arranged in a common-base configuration with zero phase shift, and means to provide a pick-up signal from the coil to the first transistor, wherein the coil, the direct current source and the emitter-collector paths of the first and second transistors are in series in regard to current.

8. A timepiece as in claim 7, wherein the means to provide the pick-up signal to the first transistor is a capacitor connected between the coil and the base of the first transistor.

9. A timepiece as in claim 8, wherein the circuit is a self-vibrating multivibrator whose self-vibrating frequency is below the natural frequency of the mechanical oscillator.

References Cited UNITED STATES PATENTS 3,131,362 4/1964 Dersch 331- 3,046,460 7/1962 Zemla 318-128 XR 3,061,796 10/1962 Schoninger 331-116 XR 3,100,278 8/1963 Reich 318-132 XR 3,124,731 3/1964 Eysen et a1. 318-132 3,238,431 3/1968 Raval 318-130 FOREIGN PATENTS 921,948 3/ 1963 Great Britain.

MILTON O. HIRSHFIELD, Primary Examiner.

D. F. DUGGAN, Assistant Examiner. 

